Vernier control for a stepper motor

ABSTRACT

A multi-position switch is connected between the windings of a stepper motor and a pair of triggers which are connected to operate in a reflected binary mode for sequentially energizing the windings of the motor in response to a series of motor advance pulses causing the motor to advance in a stepwise fashion. The multi-position switch has one pole connected to each output of the triggers and has the different positions of each pole so connected to a different motor winding that movement of the switch in one direction causes the motor to advance one step for each position and movement in the other direction causes it to reverse one step for each position.

United States Patent 9 Barcomb et al.

[451 Feb. 26, 1974 VERNIER CONTROL FOR A STEPPER MOTOR Inventors: James G. Barcomb, Endicott; John Mako, Vestal, both of N.Y.

Assignee: International Business-Machines Corporation, Armonk, N.Y.

Filed: Dec. 14, 1972 Appl. No.: 315,063

US. Cl. 318/696 Int. Cl. G05b 19/40 -Field of Search 318/138, 254, 685, 696

References Cited UNITED STATES PATENTS 3/1966 Welch 318/696 6/1967 Marakis 318/696 4/1971 Agin 318/696 Primary Examiner-Bernard A. Gilheany Assistant ExaminerThomas Langer Attorney, Agent, or Firm-Francis V. Giolma 57 ABSTRACT A miilti-position switch is connected between the windings of a stepper motor and a pair of triggers which are connected to operate in a reflected binary mode for sequentially energizing the windings of the motor in response to a series of motor advance pulses causing the motor to advance in a stepwise fashion. The multi-position switch has one pole connected to each output of the triggers and has the different positions of each pole so connected to a different motor winding that movement of the switch in one direction causes the motor to advance one step for each position and movement in the other direction causes it to reverse one step for each position.

6 Claims, 5 Drawing Figures l VERNIER CONTROL FOR ASTEPPER MOTOR BACKGROUND OF THE INVENTION locking switch means 14-17 responsive to input pulses to sequentially energize the motor windings A-D.

U. S. Pat. No. 3,324,369 which issued on June 6, 1967 to M. J. Markakis discloses the use of logic means 50 in conjunction with a reversing switch 45 for stepping a motor clockwise or counterclockwise.

SUMMARY OF THE INVENTION Generally stated it is an object of this invention to provide an improved vernier control for a stepper motor. I

More specifically it is an object of this invention to provide a manual switch for incrementing a stepper.

motor without altering the normalstepper motor drive triggers from their reset position.

It is an object of the present invention to provide for using a single multi-pole multi-position switch for operating stepper motor independently of the usual drive triggers.

Yet another object of the invention is to provide for using 'a single-pole multi-position switch with logic circuits for incrementing a stepper motor without changing the reset condition of the usual drive triggers.

Still another object of the invention is to provide for DESCRIPTION OF A PREFERRED EMBODIMENT Referringto FIG. 1 the reference numeral 10 denotes generally a stepper motor of the type described in the AIEE paper No. 61-650 presented at the AIEE Northeastern District Meeting, Hartford, Connecticut May l7l9, 1961 and entitled Characteristics of a Synchronous Conductor Motor" by Arthur E. Snowden and Elmer W. Madsen. The motor 10 has bifilar windings 10a, 1017, 10b, 10b which are connected at one end through resistors R1 and R2 to a positive source of voltage. The other ends of the windings are connected by means of drivers 120, 12H, 12)), 12b to ground. The drivers are controlled by four predrivers 16A 16A, 16B and 1613 in response to selec tive energization from the on and off outputs A, A, B, B of a pair of triggers 18A and 18B which are connected to step in a reflected binary code in response to motor advance pulses applied thereto through an inverter 20.

When the triggers 18A and 18B are in the reset condition it is sometimes desirable to advance the motor one or more steps such as for positioning a form to a particular line. This is accomplished by means of a multi-pole switch 14 w hich is connected between the prederivers 1 6A, 16A, 16B, 16B and the drivers 12a, 1217, 12b, 12b. The switch 14 has four input terminals 14A, 14A, 14B, and 14E which are onnected to the predrivers 16A, 16A, 16B, and 16B respectively. A movable element of the switch has contact members 15a, 15E, 15b, 15b which are connected to the terminals 14A, 14A, 14B, and 1413 by means of common conductive segments 15A, 15A, 15B, 153 to a plurality of output terminals 14-1 through 14-16. These output ter r ninals are connected to the drivers 12a, 12a, 12b, 12b so that in successive positions of the movable switch member 15 the terminal 14A may be sequenmovinga stepper motor a predetermined number of steps without affecting the normal operating sequence of the motor triggers.

Yet another important object of the invention is to provide for bidirectional movement of a stepper motor without changing the reset condition of the motor drive triggers.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING positions.

FIG. 4 is a schematic circuit diagram of another vernier control circuit which may be used in the control system of FIG. 1 and FIG. 5 is a schematic circuit diagram of a vernier control circuit which may also be used with the motor control circuit of FIG. I.

tially connected to the drivers 12 21, 12b, 12a and 12b. Since the A and B terminals of the triggers 18A and 18B will be energized when the triggers are in the reset condition the prgdriver 168 will likewise be connected to the driver 12b 12a, 12b and 1217 in sequence. This sequen t i al energization of the windings 10a, 1051', 10b

and 1012 as the movable switch element is advanced from one position to the other, causes the stepper motor 10 to advance sequentially. The energization of the motor windings follows the pattern indicated by the curves in FIG. 3 for the different switch positions 1, 2, 3 and 4. as designated. The movable element 15 may comprise a circular insulating wafer with the contact members 1521', 15a, 15b and l5b connecting stationary segments 15A, 15A, 15B and 158 to the terminals 14-1 through 14-16 in continuous rotation.

Referring to FIG. 2 the reference numeral 10 denotes as previously a stepper motor having bitilar windings 10a, 1047, 10b and 10b which are connected through resistors R1 and R2 to a plus source of voltage +V. The other ends of the windings are connec tgd to ground by means of drivers 12a, 12T, 12b and 12b t nder the control or predrivers 16A, 16A, 16B and 16B respectively. Instead of using a multi-pole multi-posit i on switch as in FIG. 1 the drivers 12a, 1217, 12b and 12b are energized through OR circuits 24a, 24E, 24b and 243 from a plurality of A ND circuits 25Al through 25 A4, 25111 through 25A4, 25B! theough 2584 and 2581 through 25E4 under the control of a single-pole multi-position switch 22 having a movable switch arm 23 comparable to positions 22-1, 22-2, 22-3 and 22-4 to gate different advance of the switch.

Refer ring to FIG. 4 the motor windings 10a, 10Z1', 10b

I and lllb are again connected at one end to a positive source of voltage through resistors R1 and R2. The

other ends of the motor windings may b e connected b means of movable switch arms 26A, 26A, 26B and 268 to conductors 28, 29 30 and 3 1 which are respectively connected to the A, A, B, and B outputs of the predrivers.

By providing the switch member 26A with a plurality of contacts 26A] to 26A2 and the switch members 26A, 26B and 26E with like contacts which are connected in a predetermined sequential order to the conductors 28, 29, 30 and 31 movement of the switch arms 26A, 26A, 26B and 268 can be made to cause the energization of the motor windings 10a, 10a, 10b and 10b to advance in a predetermined sequence causing stepwise operation of the stepper motor.

Referring to FIG. it will be seen that a multiposition switch 30 having a movable switch arm 31 movable to engage stationary contacts 1 through 8 which are connected to logic circuitry 32 comprising a plurality of AND circuits as shown in FIG. 2 may be used to selectively contrtfl the energization of the winding a, 101T, 10b and 10b of a stepper motor 10 to advance the motor one step at a time without affecting the reset condition of the novel drive triggers.

From the above description and the accompanying drawing it will be realized that this invention provides a simple and effective method for obtaining vernier operation of a stepper motor when the normal drive triggers are in the reset condition. the motor may be advanced any number of steps without affecting the normal operation of the motor under control of the drive triggers. If the switch is operated in the reverse direction the motor operates in the reverse direction also.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. In combination with a stepper motor having an artion of said motor armature,

' switch means connected between the outputs of said bistable switching means and said winding operable with both of said bistable switching means in the off condition to different positions in sequence to sequentially connect said bistable switching means off outputs to different ones of said windings in a progressively advancing order to cause said motor armature to advance one step for each operation of said switch means without altering the off operating condition of said bistable switching means.

2. The invention as defined in claim 1 characterized by said switch means including a plurality of groups of AND gates and AND gates of each group having one input connected to a different output of said bistable switching means and having an output connected to a different one of said operating windings, and a multiposition manual switch with each position connected to provide another input for a corresponding one of said AND gates in each group.

3. The invention as defined in claim 1 characterized by said switch means comprising a muIti-pole multiposition switch with each pole connected to a different motor winding and successive positions connected to a I different one of said bistable switching means outputin the same sequence but each advanced one sequence step.

4. The invention as defined in claim 2 characterized by said multi-position switch having 2-n positions where n is the number of motor windings and also the number of bistable switching means outputs.

5. The invention as defined in claim 4 characterized by each of said bistable switching means comprising a trigger having off and on outputs connected to said operating windings by driver circuits, and said switch means being connected in series circuit relation with said trigger outputs and said operating windings.

6. The invention as defined in claim 1 characterized by said switch means comprising a four-pole fourposition rotary switch with each of said'poles connected to a different trigger output and connecting said output to a different motor winding in each position in sequence to advance said motor armature one step for each position to which said switch is advanced. 

1. In combination with a stepper motor having an armature and a plurality of operating windings with a pair of bistable switching means having an on and off condition and on and off output connected to said windings to effect energization thereof in a predetermined stepping sequence for effecting step-by-step advance motion of said motor armature, switch means connected between the outputs of said bistable switching means and said winding operable with both of said bistable switching means in the off condition to different positions in sequence to sequentially connect said bistable switching means off outputs to different ones of said windings in a progressively advancing order to cause said motor armature to advance one step for each operation of said switch means without altering the off operating condition of said bistable switching means.
 2. The invention as defined in claim 1 characterized by said switch means including a plurality of groups of AND gates and AND gates of each group having one input connected to a different output of said bistable switching means and having an output connected to a different one of said operating windings, and a multi-position manual switch with each position connected to provide another input for a corresponding one of said AND gates in eAch group.
 3. The invention as defined in claim 1 characterized by said switch means comprising a multi-pole multi-position switch with each pole connected to a different motor winding and successive positions connected to a different one of said bistable switching means output in the same sequence but each advanced one sequence step.
 4. The invention as defined in claim 2 characterized by said multi-position switch having 2-n positions where n is the number of motor windings and also the number of bistable switching means outputs.
 5. The invention as defined in claim 4 characterized by each of said bistable switching means comprising a trigger having off and on outputs connected to said operating windings by driver circuits, and said switch means being connected in series circuit relation with said trigger outputs and said operating windings.
 6. The invention as defined in claim 1 characterized by said switch means comprising a four-pole four-position rotary switch with each of said poles connected to a different trigger output and connecting said output to a different motor winding in each position in sequence to advance said motor armature one step for each position to which said switch is advanced. 